Abstract and Introduction
Abstract
Objectives To construct a risk score out of baseline variables to estimate the risk of death without prior implantable cardioverter defibrillator (ICD) in primary prevention ICD patients with ischaemic heart disease.
Design Retrospective cohort study.
Setting Tertiary care facility in The Netherlands.
Patients All patients with ischaemic heart disease who received an ICD for primary prevention of sudden cardiac death at the Leiden University Medical Center, Leiden, The Netherlands in the period 1996–2009.
Main outcome measure All-cause mortality without prior appropriate ICD therapy (anti-tachycardia pacing or shock).
Results 900 patients (87% men, mean age 64±10 years) were included in the analysis. During a median follow-up of 669 days (IQR 363–1322 days), 150 patients (17%) died and 191 (21%) patients received appropriate device therapy. 114 (13%) patients died without prior appropriate therapy. Stratification of the risk for death without prior appropriate therapy resulted in risk categorisation of patients as low, intermediate or high risk. NYHA ≥III, advanced age, diabetes mellitus, left ventricular ejection fraction ≤25% and a history of smoking were significant independent predictors of death without appropriate ICD therapy. 5-year cumulative incidence for death without prior appropriate therapy ranged from 10% (95% CI 6% to 16%) in low-risk patients to 41% (95% CI 33% to 51%) in high-risk patients.
Conclusions The risk of death without prior appropriate ICD therapy can be predicted in primary prevention ICD patients with ischaemic heart disease, which facilitates patient-tailored risk estimation.
Introduction
Large randomised trials have demonstrated that implantable cardioverter defibrillator (ICD) treatment is the treatment of choice for selected patients at high risk of sudden cardiac death (primary prevention). As a result, implantation rates in routine clinical practice have increased drastically to an estimated 275 000 devices in 2008. However, during long-term follow-up only 35% of primary prevention ICD patients will receive appropriate therapy for ventricular arrhythmias. Furthermore, clinicians have expressed concern that the number of patients needed to treat with a primary prevention ICD might be too high and that the population eligible for ICD treatment, is of such magnitude that provision of ICD treatment will strain financial resources. In addition, ICD treatment is associated with adverse events like pocket and lead related infections, inappropriate shocks, lead extractions and device replacements. Consequently, there is a strong desire to refine the current selection criteria for primary prevention ICD treatment and it would be of interest to identify those patients, currently receiving ICD treatment, who die without receiving appropriate ICD therapy and therefore do not receive a mortality benefit from ICD treatment.
Since 1996, all patients receiving an ICD at the Leiden University Medical Center, Leiden, The Netherlands, have been assessed and followed up. This thoroughly screened cohort provided an opportunity to identify ICD recipients who die without having received ICD therapy and to assess whether baseline parameters influence the risk of death without prior appropriate ICD therapy. Finally, a clinically applicable risk model is constructed to aid clinicians in individual risk estimations for primary prevention ICD patients with ischaemic heart disease.